22q11.2 duplication syndrome
| 22q11.2 duplication syndrome | |
|---|---|
| Specialty | Medical genetics  |
22q11.2 duplication syndrome is a rare genetic disorder caused by a duplication of a segment at the end of chromosome 22.
Clinical features
The most frequent reported symptoms in patients with duplication of 22q11.2 duplication syndrome are mental retardation/learning disabilility (97% of patients), delayed psychomotor development (67% of patients), growth retardation (63% of patients) and muscular hypotonia (43% of patients).[1] However, these are common and relatively non-specific indications for cytogenetic analysis, and the extent to which the duplication of 22q11.2 causes these features is currently unknown. The duplication is frequently inherited from a normal parent, so it is clear that intellectual development can be normal.
Size of duplication
Duplications of 22q11 vary in size and thereby in gene content. They include the typical common 3-Mb microduplication, 1.5-Mb nested duplication, consistent with non-allelic homologous recombination (NAHR) using distinct low-copy repeats. These microduplications likely represent the predicted reciprocal rearrangements to the microdeletions characterized in the 22q11.2 region.[2] Smaller microduplications may occur within this highly dynamic with frequent rearrangements using alternative low-copy repeats as recombination substrates within and distal to the DiGeorge syndrome region.
Origin of duplication
The majority of 22q11 duplications are inherited often from a parent with a normal or near-normal phenotype. This is in sharp distinction to 22q11 deletion syndrome where about 90% of cases are caused by mutations that occur de novo.
References
- ^ Wentzel C, Fernström M, Ohrner Y, Annerén G, Thuresson AC (2008). "Clinical variability of the 22q11.2 duplication syndrome". Eur J Med Genet. 51 (6): 501–10. doi:10.1016/j.ejmg.2008.07.005. PMID 18707033.
- ^ Ou Z, Berg JS, Yonath H, et al. (April 2008). "Microduplications of 22q11.2 are frequently inherited and are associated with variable phenotypes". Genet. Med. 10 (4): 267–77. doi:10.1097/GIM.0b013e31816b64c2. PMID 18414210.
Further reading
- Ensenauer RE, Adeyinka A, Flynn HC, et al. (November 2003). "Microduplication 22q11.2, an emerging syndrome: clinical, cytogenetic, and molecular analysis of thirteen patients". Am. J. Hum. Genet. 73 (5): 1027–40. doi:10.1086/378818. PMC 1180483. PMID 14526392.
- Yobb TM, Somerville MJ, Willatt L, et al. (May 2005). "Microduplication and triplication of 22q11.2: a highly variable syndrome". Am. J. Hum. Genet. 76 (5): 865–76. doi:10.1086/429841. PMC 1199375. PMID 15800846.
- Portnoï MF, Lebas F, Gruchy N, et al. (August 2005). "22q11.2 duplication syndrome: two new familial cases with some overlapping features with DiGeorge/velocardiofacial syndromes". Am. J. Med. Genet. A. 137 (1): 47–51. doi:10.1002/ajmg.a.30847. PMID 16007629.
- Alberti A, Romano C, Falco M, et al. (February 2007). "1.5 Mb de novo 22q11.21 microduplication in a patient with cognitive deficits and dysmorphic facial features". Clin. Genet. 71 (2): 177–82. doi:10.1111/j.1399-0004.2007.00750.x. PMID 17250668.
- Zweier C, Sticht H, Aydin-Yaylagül I, Campbell CE, Rauch A (March 2007). "Human TBX1 missense mutations cause gain of function resulting in the same phenotype as 22q11.2 deletions". Am. J. Hum. Genet. 80 (3): 510–7. doi:10.1086/511993. PMC 1821102. PMID 17273972.